Security monitoring system and method for an electric power system employing a fast on-line loadflow computer arrangement

ABSTRACT

A security monitoring system for an electric power system includes a data acquisition system and a hybrid loadflow computer arrangement. The hybrid loadflow computer in turn includes an analog network simulator and a digital computer which processes and operates upon acquired on-line data and operator data related to the power system loadflow problem. The analog simulator includes modular circuits representative of power system busses and lines and the interface between the digital computer and the analog network simulator is provided by analog-to-digital and digital-to-analog converters and by line outage contact closure outputs. The hybrid arrangement operates iteratively to provide loadflow solutions, with the analog network simulator providing a bus voltage solution for a set of network simultaneous equations and the digital computer providing bus load and generation injection current calculations and convergence steering control. Because loadflow solutions are generated cyclically and contingency case loadflow solutions are generated with the use of basecase data modified to reflect the contingencies. Modifications are also made in the analog simulator to reflect the contingencies.

United States Patent [191 Egelston et al.

[ SECURITY MONITORING SYSTEM AND METHOD FOR AN ELECTRIC POWER SYSTEM EMPLOYING A FAST ON-LINE LOADFLOW COMPUTER ARRANGEMENT lnventors: David M. Egelston, Pittsburgh, Pa.;

Jerry C. Russell, Minneapolis, Minn.

[73] Westinghouse Electric Corporation,

Pittsburgh, Pa.

Filed: Aug. 26, 1971 Appl. No.: 175,292

Assignee:

US. Cl. 235/l51.21; 444/1; 307/43; 307/52; 307/57; 340/1726 Int. Cl. G06g 7/62; H05k 1/00 Field of Search 235/l5l.2l, 150.5, 184, 235/185; 444/1; 307/43, 52, 57; 290/40; 340/1725 References Cited OTHER PUBLlCATlONS [45] May 27,1975

Primary Examiner-Eugene G. Botz Assistant ExaminerEdward 1. Wise Attorney, Agent, or Firm-45. F. Possessky [57] ABSTRACT A security monitoring system for an electric power system includes a data acquisition system and a hybrid loadflow computer arrangement. The hybrid loadflow computer in turn includes an analog network simulator and a digital computer which processes and oper ates upon acquired on-line data and operator data related to the power system loadflow problem. The analog simulator includes modular circuits representative of power system busses and lines and the interface between the digital computer and the analog network simulator is provided by analog-to-digital and digitalto-analog converters and by line outage contact closure outputs. The hybrid arrangement operates iteratively to provide loadflow solutions, with the analog network simulator providing a bus voltage solution for a set of network simultaneous equations and the digital computer providing bus load and generation injection current calculations and convergence steering controlv Because loadflow solutions are generated cyclically and contingency case loadflow solutions are generated with the use of basecase data modified to reflect the contingencies. Modifications are also made in the analog simulator to reflect the contingencies.

14 Claims, 43 Drawing Figures ANALOG es 30 n z wgg seusons 25 GROUP II2\ "O NEW HAM psm DATA ACQUISITION REG'ONAL Co lifl l lil l ER c b n i bi s igr'izin PERIPHERALS SECURITY COMPUTER 68 x I CONTROLLABLE 52 g 5 72 n DEVICES GROUP DATA MEMORY ggl sfilgb m 70 74 SFSfiih 836%? s COMPUTER COMPUTER 60 ENSORS IAIENTED IIAYZT ma SEGSSGO SHEET 5 66 ANALOG 302 NETWORK SENSORS SIMULATOR 2S /62 DATAGECOOULZSITION N NP Ew RE PERIPHERALS ECuRITY COMPUTER MPuTER CONTROLLASLE 26??? 5 72 OEvICEs GROUP OATA MEMORY g s gfi I 70 F 74 REGIONAL MAINE DISPATCH A GROUP SENSORS COMPUTER COMPUTER 50 Fl G. 2

ANALOG NETWORK SIMULATOR IIO I REGIONAL PERIPHERALS SECURITY COMPUTER l II3 28%? 2Q FIG .3 A MEMORY II I 204 REGIONAL REGIONAL OATA DISPATCH ACQUISITION COMPUTER Q SYSTEMS NOTE- EIRST ITEM IN BLOCK IS METER POINT FIG.3C FIG. 30 LEGENDS:

ae ITEMS INCLUDED IN BACKUP TELEMETERING SYSTEM OATA CHANNELS BETWEEN NEPEx ANO SATELLITES FIGSE TELEMETEREO TO SATELLITE FROM METERING POINT ANALOG OATA RELAYEO TO NEPEx ANO NYPP F|G.3F

l PATENTEUIIIIYN I975 3 5 330 SHEET 7 MERRIMAOK MANCHESTER SCOBIE UNIT I MW HZ SANDY POND 326 II 2Mw TOTAL SATELLITE MW ll MVAR QENERATION MVAR ZMVAR K Q' QQN POwNAL 39l VOLTAGEUIS KV) ACTUAL Mw E JC A253 NET INTEROHANGE ME 'Z MvAR Mw mm W. MW MvAR VOLTAGE(345KV) 345/H5KV TR MW MvAR MONADNOCK 62 al To M55155 POWER STATION am MVAR NEw HAMPHIRE 4 (P S N u 5 u HUDSON rIE To NEESYS' DIGITAL COMPUTER u g MVAR WAR :3 :1 g 1: ll 6 ll GARvINS voLTAGE IIsKv VOLTAGEHSKV THREE RIv ERS- wHITEFIELD TIE TO CMP vOLTAGE H5 KV Q:(25O8I I97 TOTAL) MW WEBSTER MvAR GE U VOLTA 2'4 TEL% E T E RING ALL 'TEMS SYSTEM MARKED 2|6 4| YAR MOUTH -222 BUCKS PORT l F209 UNIT I Mw TIE TO BANGOR BACEKUP ALL ITEMS 2 HYDRO 2) TELEM EQ' MARKEDY II 3 ll 224 nny/R SYST POWNAL MASON 34V?(/Hg KK\\;)TR UNIT2 MW '226 M II II MvARIIISKv) 5 345/ll5 KV TR. GUILEORD I 1 -MW(ll5KV) 3%, To BANGOR HYD. CENTRAL MA|NE POWER. MVAR(H5 KV) MvAR &Z L223 MAINE YANKEE HARRIS HYDRO 1 UNIT I MW VOLTAGE(345KV) UNITS POWNAL 3 I? I,2 S 5 Mw Mw MvAR wYMAN HYDRO B w UN'TS g MVAR F|G.3D 3 MW AUGUSTA H2 UN w K TOTAL SATELLITE [aANGoR NEw BR S Ic L GENERATION MW \i. TOTAL G NTROL GENERM ION \L ACTUAL SATELLITE NET INTERGHANGE FRI'ENTEUIIAYN 1975 3,886,330 SHEET 1 O 505 4 PROGRAMMER'S ,509 53 CONSOLE PAPER TAPE W TYPEWRITER PUNCH 536 soI aREADER [5H WW2 cARD PUNCH PROGRAMMERS 535 r a READER cONsOLE I TYPEwRITER PUBLIC cm I 503 mm PUNCH a READER 498 ALARM 532 SECURITY DISPATCH cOMPuTER E62? COMPUTER TYPEwRITER LINE 4 CENTRAL MEMORY cENTRAL PRINTER PROcEssOR PROcEssOR 5% HO III 06 ANALOG 50o TYPEWRITER NETWORK INPUT/OUTPUT S|MULATOR T INTERFACE 5|? PUSH PANELS W BuTTON 495 I cONsOLE LINE I 502 OUTAGE INPUT/OUTPUT C60 491 INTERFACE 507 PANELS 5'5 '%'5fib%"k- CARD PUNCH r496 a READER DATA LINK ANALOG/DIGITAL CONVERTER F364 A MEMORY ORGANIZATION 52|-- FOREGROUND 5 2- FOREGROUND SECURITY 2 coMPuTER SSM COMMON SHARED SECURITY H3 cORE a DIsPATcH MEMORY COMPUTERS p FOREGROUND gi Jf FIGAB REAL BUS VOLTAGE OUTPUTS SHEET CURRENT INPUTS IMAGINARY INJECTION FATEPT?! FIGBA S J J J J Y m m m m m m m m m T R R R R R R R R G T 0 Am 0 c 2 MC 3 4 5 6 7 B 9 n v W H l H H H H H H H H H SHEET PATENTEDMAY 27 ms FIGYA 2 7 8 m H AL 9 wmmnm B R W. P R 2 I m R REAL BUS VOLT INPUT ARMS AR E :05

PIO2 Rm IMAGINARY BUS VOLT INPUT AR I02 PATENTE'l-iaa 27:95 3,886,330

SHEET 1 mrmmv [m 3 ,886,330

SHEET 16 R25 INJECTION ""l CURRENT H|4 MW-- H|6o-wo z CURRENTS 'UMAOINARYDOT 366 REF, VOLTAGE OUT (TO UNES) FROM 1/0 T0 T0 LINE iL FROM BUS LINE U5 MODULE FROM [/0 :jMOOuwI FROM I/O FROM i FROM FROM 8 I/O 1/0 1/0 1 M55? 1 & BUSSES S LINE MOD LE -MODULE FROMI/O (TRANSFORMER) l l A LiNE l MODULE BUS FROM 1/0 -MODULEBLOS FIG. 9

PAIEIIIIIIIIIm I915 3,888,330 SHEET 17 CONVEX REMVEC NH MAINE NEPEX ACTION BUTTONS VERIFY ENTER OUTPUT CANCEL CLEAR CONSOLE. CRT DIGITAL DEVICE TYPER DISPLAY ON/OFF CRT UP DATE INHIBIT DECIMAL 2 3 PT FIG.| I 

1. A security monitoring system for an electric power system comprising a security loadflow computer including an analog network simulator and a programmed digital computer, means for generating signals representing predetermined on-line system data including at least some unit generator and tieline power values and at least some bus voltage values, means for applying said data signals to said digital computer, said digitial computer including means for storing said predetermined on-line data, said analog simulator including a plurality of bus DC circuits and line DC circuits interconnected to correspond to the AC network, said digital computer including means for geneRating representations of bus generation and load currents as a function of predetermined parameters including stored bus power and voltage data, an analog output system, said digital computer further including means for causing said output system to generate phasor current signals representative of the digital computer determined bus generation and load currents, means for applying the phasor bus generation and load current signals to the corresponding bus DC circuits, each of said bus DC circuits including means for responding to line phasor current and bus generation and load phasor input current signals and for generating an output bus voltage phasor signal, each of said line DC circuits including means for responding to the difference between applied bus voltage phasor signals and generating an output line phasor current signal in accordance at least with a representation of the equivalent series branch line impedance, said digital computer further including means for generating representations of bus voltage phasor signals after the generation and load phasor current signals are applied to said DC bus circuits, means for generating representations of bus generation and load current values in successive iterations after a startup iteration as a function of bus voltage values determined in the next preceding iteration, means for converging the iterative process to a solution and for sensing when a solution is reached and means for monitoring representations of predetermined solution parameters and generating alarms under predetermined conditions.
 2. A security monitoring system as set forth in claim 1 wherein means are included in said digital computer for providing on-line basecase loadflow solutions cyclically and for providing contingency case loadflow solutions in the time periods between on-line loadflow solutions.
 3. A security monitoring system as set forth in claim 2 wherein means are included in said digital computer for determining and running contingency cases in accordance with predetermined rules applied to the results of next preceding basecase loadflow solution.
 4. A security monitoring system as set forth in claim 3 wherein means are included in said digital computer for receiving operator specified contingency cases and for generating contingency case data for the contingency case loadflow solutions on the basis of data employed in the next preceding basecase solution and on the basis of the specified contingency events in the contingency case to be run.
 5. A security monitoring system as set forth in claim 2 wherein one set of contingency events includable in contingency cases are line outages, and means are included in said digital computer for determining line outages and for disconnecting determined outage lines from said analog simulator.
 6. A security monitoring system as set forth in claim 2 wherein means are included in said digital computer for generating contingency case data for the contingency case loadflow solutions on the basis of data employed in the next preceding basecase solution and on the basis of the specified contingency events in the contingency case to be run.
 7. A security monitoring system as set forth in claim 6 wherein means are included in said computer for modifying basecase data for generation unit losses in accordance with a predetermined basis for allocation of lost power.
 8. A security monitoring system as set forth in claim 6 wherein means are included in said digital computer for modifying basecase data for tieline losses in accordance with a predetermined basis for allocation of lost power.
 9. An automated method for monitoring the security of an electric power system comprising the steps of sensing at least some on-line parameter values including at least some on-line unit generation power and bus voltage values for the system, applying said sensed on-line values to an input of a digital computer and storing representations of said on-line vlaues therein, operating the digital Computer to determine bus generation and load current values as a function of stored bus power and voltage data, applying phasor signals corresponding to the bus generation and load current values in said computer to an analog network simulator which includes DC bus circuits and DC line circuits interconnected to simulate the power system, operating the analog simulator to cause the bus circuits to generate solution bus voltage phasor signals, and operating the digital computer to determine new bus generation and load current values as a function of the stored data and the solution bus voltage phasor signals, and operating said digital computer to monitor predetermined solution parameters and to generate alarms under predetermined conditions.
 10. A method as set forth in claim 9 wherein the steps further comprise operating said digital computer to provide on-line basecase loadflow solutions cyclically and to provide contingency case loadflow solutions in the time periods between on-line loadflow solutions.
 11. A method as set forth in claim 9 wherein the steps further comprise operating said digital computer to generate contingency case data for the contingency case loadflow solutions on the basis of data employed in the next preceding basecase solution and on the basis of the specified contingency events in the contingency case to be run, operating said digital computer to determine and run contingency cases in accordance with predetermined rules applied to the results of next preceding basecase loadflow solution, and operating said digital computer to accept operator specified contingency cases.
 12. A method as set forth in claim 9 wherein the steps further comprise operating said digital computer to modify basecase data for contingency power losses in accordance with a predetermined basis of allocation.
 13. An automated method for monitoring the security of an electric power system comprising the steps of sensing at least some on-line power and bus voltage values for the system, storing said sensed on-line values in loadflow computer, operating the computer to determine loadflow solution parameters including line currents and bus voltages as a function of stored bus power and voltage data, operating the computer to monitor and alarm predetermined solution parameters, operating the computer to provide on-line base-case loadflow solutions cyclically and to provide contingency case loadflow solutions in the time periods between on-line loadflow solutions.
 14. A method for monitoring the security of an electric power system as set forth in claim 13 wherein the method steps further comprise operating said computer to determine and run contingency cases in accordance with predetermined rules applied to the results of the next preceding basecase loadflow solution, and to accept operator specified contingency cases, and to generate contingency case data for the contingency case loadflow solutions on the basis of data employed in the next preceding basecase solution and on the basis of the specified contingency events in the contingency case to be run. 